1. Field of the Invention
The present invention relates to an adaptive equalizer and more particularly, to an adaptive equalizer including a speculative decision feedback equalization circuit.
2. Description of the Related Art
According to speeding up of an information communication apparatus, a transfer rate (data rate) of data transferred between semiconductor devices configuring the information communication apparatus increases. For example, it is predicted that a transfer rate per channel transferring data reaches 25 Gbps in 2016 and the transfer rate becomes faster. The semiconductor device is mounted on a substrate such as a printed substrate and data is transmitted and received via a wiring line of the substrate. In this case, the wiring line of the substrate functions as a transmission line to transmit data. However, there is transmission loss in the transmission line. For this reason, when the transfer rate of the data transmitted by the transmission line increases, the transmission loss also increases.
When data is transferred at a high transfer rate using the transmission line, inter-symbol interference occurs due to the transmission loss and the reflection in the transmission line and a waveform of the data is deteriorated. Particularly, if the transmission line is provided over a long distance, deterioration of the waveform of the data increases and it becomes difficult to transfer the data at the high transfer rate.
As technology for reducing the deterioration of the waveform due to the inter-symbol interference, equalizers are known. As the equalizers, there are multiple types of equalizers including an adaptive equalizer. If the equalizer is used, the inter-symbol interference can be suppressed and the data can be transferred at the high transfer rate in the transmission line of the long distance or the transmission line with the reflection. JP-2011-151765-A discloses technology for a decision feedback equalizer as the equalizer.